Submitted by Sturmwolken t3_11337v9 in askscience
For the record, I am a 1st Year College Student who is taking a Chemistry class. This was a practice question I was extremely curious and wanted to learn more about.
We were practicing fairly basic chemical equations in my Chemistry class when the equation of Fe3O4(s) + H2(g) -> Fe(l) + H2O came up. Fairly simple in terms of chemical balancing, but the actual mechanics of the reaction confused me. I cannot find any explanation of this reaction anywhere I look.
My assumption would be that Iron(II,III) Oxide, when heated to near its melting point, becomes reactive enough to interact with hydrogen gas in the air, stripping it of Oxygen atoms and forming water vapor, thus creating pure Iron which then melts due to having a lower melting point than Iron(II,III) Oxide. However I am unsure and can't find anything to back this claim/assumption.
If anyone more capable in this subject then me could answer my question I would be extremely grateful.
JonseyCSGO t1_j8ojcm8 wrote
From the equation you've posted you're reacting magnetite with hydrogen gas directly, and generating water vapor and iron as your end products. It's been ages since I calculated enthalpy, but quick searches say you'll need to put in 150kJ of energy per mole reacted.
Said differently, in boring conditions, wet iron rusts, sometimes into magnetite and if it does so, it will evolve off hydrogen gas.